Quadmesh

Michael D. Sumner

2018-06-13

quadmesh

Build a “quadmesh”" in R.

library(quadmesh)
library(raster)

## Loading required package: sp

data(volcano)
r <- setExtent(raster(volcano), extent(0, 100, 0, 200))


qm <- quadmesh(r)

library(rgl)

## Warning in rgl.init(initValue, onlyNULL): RGL: unable to open X11 display

## Warning: 'rgl_init' failed, running with rgl.useNULL = TRUE

scl <- function(x) (x - min(x))/diff(range(x))
shade3d(qm, col = grey(scl(qm$vb[3,qm$ib])))

rglwidget()

A “quadmesh” is a dense mesh describing a topologically continuous surface of 4-corner primitives. I.e. a grid, without the “regular”. This is useful particularly when combined with map projections and texture mapping.

We are not limited to a regular grid, trivially let’s distort the mesh by a weird scaling factor.

The topology of the grid is still sound, but we are no longer bound to the regular constraint.

qm <- quadmesh(r)

qm$vb[1,] <- qm$vb[1,] * qm$vb[2,]/54
open3d()

## null 
##    3

shade3d(qm, col = grey(scl(qm$vb[3,qm$ib])))

rglwidget()